This invention relates to an earth moving machine, that is a machine having a body movable by its own propulsion means over the ground, and a boom mounted on the body, the boom and/or an additional arm mounted thereon, commonly known as a "dipper" arm carrying an excavating implement, the body and/or boom and/or dipper arm and/or excavating implement being relatively movable to enable operations to be carried out, such as earth moving by the implement.
In use of such a machine, it will be appreciated that the postion of the centre of gravity of the machine will shift as the implement is loaded and unloaded, and as the boom is moved relative to the body of the machine, but particularly when the dipper arm is moved relative to the boom to move the implement relative to the body.
Careful attention has to be given, when designing an earth moving machine, to ensure the stability of the machine during operation and particularly to ensure that the machine cannot tip forwardly when the implement is fully loaded and in an outermost position.
It has been proposed to provide a counterweight which can be moved to compensate for these shifts in centre of gravity. One arrangement is shown in Canadian specification CA No. 1008107. In this arrangement the boom is coupled to the counterweight by a mechnaical linkage such that any movement of the boom relative to the body results in a proportional movement of the counterweight.
The counterweight is mounted on a base frame of the machine thus giving good lateral stability, but the machine has distinct disadvantages. Particularly, movement of the counterweight is not in response to movement of the centre of gravity of the machine, which as mentioned above, is caused in the main when the dipper arm is moved relative to the boom.
Further, the boom comprises two mutually pivoted parts each connected by its own hydraulic ram to the body so that the boom parts may move relative to one another. The mechanical linkage which connects the boom ot the counterweight, only moves the counterweight when the first boom part i.e. that boom part nearest the body, moves relative to the body. In practice, because of the articulation of the implement which can be achieved moving only the second boom part and the dipper arm, movement of the first boom part and hence of the counterweight, may not often occur. Hence the counterweight is ineffective.
Accordingly, it is an object of the present invention to provide a new or improved earth moving machine which overcomes these disadvantages and provides additional advantages.